US Secretary of State John Kerry says the Islamic State can be defeated in "months" if a ceasefire is reached between Syria's government and moderate rebels.
Kerry says air power alone won't be enough. He says the campaign will require local Syrian and Arab ground forces, too.
Kerry says it is important for the world to secure a ceasefire in Syria and a political transition.
He believes that would allow the "scourge" of IS to be eliminated much faster.
The US has spoken generally of degrading and eventually destroying the group. It has tried to avoid timelines.
Kerry was speaking Thursday at a European security conference in Belgrade, Serbia.